Analytical model for residual stresses in polymeric containers during cryogenic storage of hematopoietic stem cells

Hematopoietic stem cell (HSC) therapy can significantly lower instances of infection in chemotherapy patients by accelerating the recovery of white blood cells in the body. However, therapy requires that HSCs be stored at cryogenic temperatures to retain the cells’ ability to proliferate. Currently, cells are stored in polymeric blood bags that are subject to fracture at the extremely low storage temperatures, which leads to cell contamination, thereby reducing their effectiveness. Therefore, we have developed an analytical model to predict the accumulation of stresses that ultimately lead to crack initiation and bag fracture during cryogenic storage. Our model gives explicit relationships between stress state in the container and thermoelastic properties of the container material, container geometry, and environmental factors that include temperature of the system and pressure induced by excess gas evolving from the stored medium. Predictions based on the model are consistent with experimental observations of bag failures that occurred during cryogenic storage applications. Finally, the model can provide guidance in material selection and bag design to fabricate bags that will be less susceptible to fracture.